1. Field of the Invention
The invention relates generally to dentistry and more specifically to articulators used with cast dental models that assist doctors and technicians in the construction of prosthetic dentures or denture elements by providing a model for fitting outside the patient's mouth.
2. Description of the Prior Art
Many different types of articulators have been commercially available for several years and are sold throughout the world. Articulators, or correlators as they are sometimes called, range from very simple to very complex devices. Disposable models exist as do models designed for re-use. Some articulators are capable of simulating the full range of occlusal and masticatory registrations observed in the patient population. A lack of such registration capabilities can often lead to inconveniencing the patient by requiring several visits for fitting. Simple articulators are easy to use but have a limited range of registrations. Complex articulators have a wide range of registrations, but are so difficult to use that formal training of the users is necessary. Either extreme results in higher costs for everyone involved.
Beyond simulating occlusal and masticatory registrations, an articulator should allow the inside area of the casts to be accessed. One way to do this is to hinge the upper cast to the lower cast FIGS. 1 shows a prior art method of doing this, that is disclosed in U.S. Pat. No. 4,382,787 issued May 10, 1983 to Huffman. FIG. 1 is an assembly, referred to by the general reference numeral 10, comprised of an upper cast 11, a lower cast 12, and an articulator 13. The articulator has a pair of mounts 14, a pair of ball joints 15, and a pair of hinges 16. The hinges 16 allow the distance between the mounts 14 on casts 11 and 12 to be adjusted. Articulator 13 is a disposable type, because ball joints 15 are intended to be adhesively locked after casts 11 and 12 are registered. Locking ball joints 15 prevents articulator 13 from being reused.
FIG. 2 is a prior art non-disposable articulator, referred to by the general reference numeral 20, and is similar to a type manufactured by Crescent Dental Manufacturing Company (Lyons, Ill.) under its "Flexi" trademark. Articulator 20 is a very simple device made of wire that has a pair of springs 22, a pair of hinges 24, an upper U-frame 26, and a lower U-frame 28. U-frames 26 and 28 are intended to be inserted into sockets in upper and lower dental casts (e.g., casts 12 and 14, respectively). The sockets are then plastered to retain articular 20. Articulator 20 cannot be removed from the casts without ruining the casts. Access to the inside area of the casts is possible by swinging upper U-frame 26 away from lower U-frame 28 on hinges 24. Articulator 20 does not allow a full range of registration, and the sockets in the casts intended to receive U-frames 26 and 28 must be precisely positioned. To remove articulator 20 from the casts, the casts probably will suffer some damage and this is certainly not a procedure that is likely to be attempted more than once.
A correlator similar to that of FIG. 2, but with several more complex features, is described in U.S. Pat. No. 2,430,177, issued Nov. 4, 1947, to Johnson, et al. A piano type hinge with an axle having the appearance of a cotter-pin joins two dental casts through four pins inserted into the casts, two in the upper cast and two in the lower cast. The cotter-pin axle allows the correlator to be separated by withdrawing the axle from the hinge, and it also allows the casts to be pivoted into an open position. Four wire helixes between each pin that enters into the casts and the hinge give some flexibility in the assembly. The correlator lacks a means to adjust the height of the upper cast to the lower cast and therefore makes the placement of where the pins enter the casts very critical. The method of holding the pins in, while removeable, is not as convenient, nor is it as easy to separate as the present invention, described below.